Boost C++ Libraries

...one of the most highly regarded and expertly designed C++ library projects in the world. — Herb Sutter and Andrei Alexandrescu, C++ Coding Standards

Wait for the socket to become ready to read, ready to write, or to have pending error conditions.

void wait(
    wait_type w);

This function is used to perform a blocking wait for a socket to enter a ready to read, write or error condition state.

Waiting for a socket to become readable.

boost::asio::ip::tcp::socket socket(my_context);
...
socket.wait(boost::asio::ip::tcp::socket::wait_read);